iphone autodimming question

I can't get this to work propperly, it was ok on my iphone 4 on ios 5, but then the way the dimming works changed(don't rember which ios, but it's the same with my current ip5 running ios 6.0.1)
From what I've read, when you use autodim and adjust the slider to a certain level it would remenber the setting. For example if my room is totally dark I want the slider to be all the way down, but during daytime I want it about 2/3 way up. But, if I adjust the dimming at the daytime level and then turn on the phone at the nighttime level it won't go all day way down on the slider, causing my eyes to hurt .
What I want is the screen to be at it's lowest level in total darkness, but 2/3 during daytime, can't seem to find a way to do this without manually adjusting the level, which makes the autodim function kind of useless .

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